Who's altering display? (4)
I believe the answer is:
show
'display?' is the definition.
(I know that display is a kind of show)
'who's altering' is the wordplay.
'altering' is an anagram indicator.
'whos' with letters rearranged gives 'SHOW'.
(Other definitions for show that I've seen before include "Expose" , "charade" , "Exhibit - present" , "Labour's evidence for starting" , "Demonstrate - parade" .)